1. Field of the Invention
The present invention relates to systems and methods of agricultural irrigation. More specifically, the present invention relates to systems and methods of automatic agricultural irrigation in response to varying moisture demands within the area to be irrigated.
2. Description of the Prior Art
Conventional systems and methods of agricultural irrigation involve the use of a water supply source supplying water through a relatively large diameter pipe over a relatively short period of time. In this type of system, a pressure gradient is set up wherein the dispensing devices closest to the water supply are operated at a higher pressure than the dispensing devices further away from the water supply. Since most dispensing devices, such as sprinklers, operate optimally within a given pressure range for a given volume flow rate, it would be desirable to have a system where each individual dispensing device was operated at its particular optimal pressure. This would ensure predictable water distribution patterns which would be reproducible and would also be helpful in planning the irrigation system.
A major cost of conventional irrigation systems is the pipe for distributing water from the water supply source to the dispensing devices. Substantial cost savings could be realized if the diameter of the distributing pipe could be reduced without reducing water volume to the dispensing devices while they are operating. Additionally, it would be desirable to operate the dispensing devices in response to the moisture demands of each dispensing device's environment.
An adequate irrigation system could be devised where different portions of the system being supplied by a single water supply source are operated individually in response to the moisture demands of the environment of the portion while maintaining water pressure within the portion at an optimal level. However, the best irrigation system would involve the individual automatic operation of each dispensing device in response to the moisture demand of its environment with a pressure limiting device for allowing operation of each dispensing device only at or above optimal operation water pressure.
Operation of such a system in agricultural settings such as lawns, golf courses, agricultural fields and even areas of trees or plants which may be potted or planted, raises a practical problem of how to provide for such individual automatic operation. Certainly, electrical switching means could be utilized, however, water operated control devices such as that disclosed in my prior application for U.S. Letters Patent Ser. No. 499,485 filed Aug. 22, 1974 and now U.S. Pat. No. 3,981,446 entitled "WATER OPERATED CONTROL APPARATUS AND METHOD" would be particularly suited for use in this type of irrigation system. In this patent, I disclosed a water operated control apparatus and a method for operating a controlled device wherein the water operated control apparatus was associated with a moisture sensing apparatus such as a porous ceramic or plastic material with the ability to pass air or not depending upon the amount of water saturation therein. Although this device is commonly used for operating numerous types of devices and valves, heretofore, it has not been used in combination with a pressure sensor for individual operation of dispensing devices, such as sprinklers, within an irrigation system, as is contemplated herein.